Existing start/stop strategies for heating, ventilation, and air conditioning (HVAC) systems are based on fixed start/stop schedules, gradient methods, and unoccupied setpoint adjustment methods. These strategies estimate the start/stop times for an HVAC system required to meet comfort conditions at the beginning and end of daily building occupancy. The gradient method predicts the required start time for the HVAC system based on a single linear approximation of the indoor temperature, at the beginning or end of the occupancy period. An example of the gradient method is described in U.S. Pat. Nos. 4,660,759 and 4,106,690. The setpoint adjustment method regularly updates the unoccupied setpoints of the HVAC system to reach the required comfort setpoint at the beginning or end of the occupancy period. An example of the setpoint method is described in U.S. Pat. No. 1,463,988. However, these methods do not take into account zone and outdoor air temperatures forecasting or HVAC equipment efficiency, which may result in comfort violations and increase energy usage.
Accordingly, it is desirable to provide a control system to improve HVAC system efficiency and maintain building comfort levels.